The present invention is concerned with hot-melt dispensers for melting rods of thermoplastic material and dispensing and applying the resulting hot-melt materials, and more particularly is concerned with hand-held glue-guns.
In our European patent specification 0 257 838 (U.S. Ser. No. 249,237) is described and claimed, a hot-melt gun provided with trigger-operated feeding means for feeding a solid rod of thermoplastic material to the melt-chamber of said hot-melt gun is characterised by a positive feed mechanism comprising at least one driven elongated feed member controlled by drive means operated by the trigger, said elongated feed member comprising a driven continuous feed-belt arranged with its longitudinal axis parallel to the axis of the rod of thermoplastic material being fed to the melt-chamber. The feed-belt may be arranged so that one outer face contacts the rod along a substantial part of its length. Preferably a second belt is arranged in parallel to contact the opposite side of the rod so that the rod is engaged between the two parallel belts. The second belt may also be driven either by the same motor that drives the feed-belt or by a separate motor or it may function as an idler.
The driven belts may be powered by any suitable means e.g. by hydraulic, pneumatic or clockwork devices but are preferably electrically driven by electric motors which can be arranged to drive one or more belts. The trigger may control the operation of the motor by conventional switching arrangements and these may incorporate control elements such as electronic computer chip devices. Such devices facilitate control of feed rate, can enable pre-set amounts to be extruded and also provide safeguards against overload pressures, over-heating, operation at below optimum temperature and similar undesirable conditions.
Throughout these specifications, the term "belt" is used to include all similar, continuous structures such as chains which are equally effective. For example, a so-called gripper chain lends itself very well to the incorporation of outfacing stud elements to form a hook-belt.
It is an object of the present invention to improve the design and operation of a glue-gun provided with belt-feed according to European patent specification